linux-kernel - Re: [PATCH] book3s_hv_rmhandlers:Pass the correct trap argument to kvmhv_commence

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Message-ID: <20150817055345.GA13304@in.ibm.com>
Date:	Mon, 17 Aug 2015 11:23:45 +0530
From:	Gautham R Shenoy <ego@...ux.vnet.ibm.com>
To:	Sam Bobroff <sam.bobroff@....ibm.com>
Cc:	"Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	kvm-ppc@...r.kernel.org,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: [PATCH] book3s_hv_rmhandlers:Pass the correct trap argument to
 kvmhv_commence_exit

Hi Sam,

On Fri, Aug 14, 2015 at 03:07:28PM +1000, Sam Bobroff wrote:
> On Thu, May 21, 2015 at 01:57:04PM +0530, Gautham R. Shenoy wrote:
> > In guest_exit_cont we call kvmhv_commence_exit which expects the trap
> > number as the argument. However r3 doesn't contain the trap number at
> > this point and as a result we would be calling the function with a
> > spurious trap number.
> > 
> > Fix this by copying r12 into r3 before calling kvmhv_commence_exit as
> > r12 contains the trap number
> > 
> > Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
> 
> Hi Gautham,
> 
> I agree with your logic: r3 is quite clearly corrupted in that path. So:
> 
> Reviewed-by: Sam Bobroff <sam.bobroff@....ibm.com>
> 
> Just one comment: Do you have a case of this causing some visible problem due
> to the corrupted trap number? (I'll test the patch if you do.)
> 

Actually no! I found this bug while reviewing the code for some other issue.

> Cheers,
> Sam.

--
Thanks and Regards
gautham.

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